Telegraph system



Feb. 19, 1935. R. G. GRIFFITH TELEGRAPH SYSTEM Filed April 25, 1951 8 Sheets-Sheet 1 INVENTOR RONALD G. GRIFFITH ATTORNEY Feb. 19,, 19359 R. G. GREl- 'FETH 3 9 TELEGRAPH SYSTEM Filed April 23, 1931 8 Sheets-Sheet 2 INVENTOR RONALD G. GRIFFITH ATTORNEY Feb. 19, 1935) R. s. GRIFFITH TEHEGRAPH SYSTEM Filed April 23', 1951 8 Sheets-Sheet 3 INVENTOR RONALD G. GRIFFITH BY ATTORNEY Feb. 19, 1935. R. G. GRIFFITH TELEGRAPH SYSTEM Filed April 25, 1951 8 Sheets-Sheet 4 INVENTOR RONALD G. GRIFFITH Y ATTORNEY .FB. 19,1935. RGGRIFFITH 1,991,978

TELEGRAPH SYSTEM Filed April 25, 1931 8 Sheets-Sheet 5 FIG 6.

,INVENTOR RONALD c. GRIFFITH ATTORNEY Feb. 19, 1935. R. G. GRIFFITH 1,991,978

TELEGRAPH SYSTEM Filed April 23, 1931 8 Sheets-Sheet 6 F/aa . INVENTOR RONALD G. GRIFFITH ATTORNEY Feb.l9, 1935. V J GR FITH 9- 1,991,978

TELEGRAPH SYSTEM Filed April 25, 19:51 Sheets-Sheet 7 9 INVENTOR RONALD c. GRIFFITH ATTQR EY Feb. 1-9, 1935.

v R. e. GRIFFITH TELEGRAPH SYSTEM Filed April 23, 1951 8 Sheets-Sheet 8 KINVENTOR RONALD c. GRIFFITH ATTORNEY Patented Feb. 19, 1935 UNITED STATES r 1,991,978 r "IEVIQEGRAPH" sYs'rEM Ronald George Griffith, Croydon, England, assignor to Creed and Company, Limited, 'Croy don, England Application April 23, 1931, Serial No. 532,225

In Great Britain May 21, 1930 20 Claims.

tral interconnectingstation. t v

The objector the invention is to provide a simple and eiiicient system in which telegraphic;

communication between stations is [effected by means of break or reduced current impulses over,

a circuit supplied with signalling current from I a source of energy at the central station.

clearing signals from a subscribers station tola central station in a system of the class referred to. H

According to another feature,"means is provided for starting a motor-for driving printing apparatus at a subscribers station upon the connection of a cord circuit at the oentralstation to the subscribers line circuit. .1, V

According to yet another feature, means isv as-" sooiated with a cord circuit at the central station for sending signalsnotifying the progress of a call, to a calling subscriber consequent upon operations performed at the central station in efperformed at the central station in accordance with the indication of a required subscriber set up on a display panel under the control of ourrent impulses from the calling'subscriber.

An alternative arrangement of a cord circuit is then shown with reference to Figs. and 6 in which the indication of a required station or subscriber is transmitted to the central station by the operation of printing telegraph apparatus normally provided at'the subscribers station for effecting telegraphic communication. The sub scribers line and terminal connections shown in Figures 3 and 4 will also serve for the cord circuit of Figs. 5 and 6 but in thiscase the subscribers impulsing dial will not be used. The

as for a trunk position at the central station. In this case the tie-line shownin Fig. (may conveniently be used for extending a calling subscriber thereto. Fig. 8 --shows arrangements" plificatiori effected in these arrangements over According to one ,featurathe invention pro vides means for sending distinctive calling and,

larlydefined inthe claims hereinafter appended.

' ries, through the following circuit:-- circuit arrangements of Figs. 5 and 6 is described which may be employed for signalling over trunk" lines between two central interconnecting stationsl H A cord circuit operating on similar general principles to that of Fig. 2 is then shown with 5 reference ,to Figs..9 and 10 with the subscribers terminal arrangements at the central station shown 'in Fig. 11 and the terminal arrangements at the subscribers station in Fig. 12. The siml0 thoseof the corresponding Figs. 1, 2, 3 and 4 render the'iarrangement suitable for a system with a limited number of subscribers lines, butit will be. clear to those skilled in the art that considerable modifications can be eifected to any 15 of the circuit arrangements shown and described in the present specification without departing from the spirit of the invention as more particu- Forflthe correct operation of many circuits-described in the present specification, it is neces: sary that certain relay tongues make contact with their front contact stops on operation 01' the armature, before breaking contact with their back contact stops. "Sucl1 relays are well known .25 V in the art. Those pairs of relay contacts shown in the present drawings which shouldlbe so arranged are indicated in the conventional manner. I Mn'rHoooF LOPERATION'OF THE Cmcnrr ARRANGE- I lvmnrs SHOWN IN Frames 1, 2, 3 AND 4 -(1)' The subscriber originating a call To call the exchange the subscriber earths the loop by operating the calling key CFK (Fig. 4) 3 Thisenergizes his calling relay A at the exchange andcauses his caHing lampCL to glow. When the calling relay A operates it looks itself in the operated condition by establishing thev following circuitz I 40 Earth, contacts B1, B2, contactsI11, I12, contacts A5, A6, windings of relayA to battery.

(2) The exchange answering a call To answer a call the exchange operator inserts an answering plug AP of a connecting cord into the line jack AJ .of the glowing""c'alling lamp. This operation'energizes the cutoff I relay B, andthe display pick-up relay C in se- From earth, through contacts I7, I6, windlngs of relay B, via the sleevelconnection of the answering plug and jack, AP, AJ,-through contacts M8, M7, windings of relay C, contacts S8 S7 to. :7:

battery;

connecting plug and jack AP, AJ, through con-.-

tacts B8, B7, contacts I9, I10, via the linethrough the subscribers equipment, back through contacts I2, I1, contacts B4 Be, the; tip, connec-i tion of the plug and jackAP, *AJ, through contacts M1 M2, contacts C2 C3, the windings of the impulsing relay D to earth. v

When current traverses this circuit the oath ing subscribers motor is started, thus giving him indication to dial the wanted number.

3) The subscriber giving the number required Having operated his 'calling key the calling subscriber then waits untilhis teleprin'ter meter s'tart's, the starting of which informs the calling subscriber j-that he is connected to the displayequipment at the exchange by means of mediaiimgurfit 'He then dials the number of the ""wa-nted subscriber.

l' he energi'zation of relay D, as above described 'in turn effects the energization of the resetting relay-E throughcontactsD2 D3. The resetting relay when energized prevents the" resetting oft-he five selector switches of "the display equipment by operating the off normal relay uirougnn'z E3, hereinafter described.

In order to display the wanted number at the-exchange the subscriber has to transmit acertain number of groups of impulses that are known to the art of automatic telephony as"dial- 'li'ng impulses, Ther'efore, in other words,fa

calling subscriber has'to dial acertainfnumberj' of fumes infor'der to "displaythe wanted "num-, her at the exchange;

These 'g'roups of impulses causerela'y D to one er'at'e a ce'r't'ain number of times. "Duringthe first gi'c'upfof impulses eachicperation "of "relay D 'o'p-. eratesfthe first number selector magnet (RQTZ),

a certain number of times determined by the number of impulses recorded on relay D. This is achievedithro1igh the renewing circuits- From contacts D1 D2, contacts- E4 windings of digit selector relay F, first, contact position of wipers W2 of the digit selector DS, windings df the'first numberselector magnet (Rx- T2) 'to battery.

The' trans'mission of thefi'rst group of impulses through thefirstnumber selector-magnet (RoTZ) causes the wipers of the first number'selector NS to he stepped round to a position determined by the number of "times RoT2 is energized. The transmission of this first group of impulses throughthe digit selectorrelay F'causes it to operate and through contacts F2 F3, complete a circuit to the driving magnet RoTl, of thejdigit selector DS;

Consequently the'number of steps made by the wiper NSl are the sameas the number of impulsesfjsignalled in 'the'group.

the end of "the transmission of'the first group. of impulses r'epresentihg' the {first digit,

thefsubscriber then operates hi'sf'dial to transmit the secon d digit. Durin'gthistime i. e. until-the release of the impulsing relay D the relay 3 E; remains' energized. When relay "F'becomes 'de-energized RoTl is also de-energized. This causes the contact arms or so called wipers of the digit selector to be stepped one division, or in other words on to their next contact.

When the calling subscriber releases the dial to transmit the second digit group of impulses, the relay F is again energized in series with the driving magnet of the selector (BOT-3 via'the second of wiper W2 of digit selector DS.

"The driving magnet (ROT3) is energized for a numberof times equivalent to the number of impulses 'transmitted'in the second group and so. steps its wipers the same number of divisions. Consequently, when the calling? subscriber is operating the dial to transmit the third group of impulses, relays D and E again remain energized; 'Relay F is again de-energized and causes the wipers of the digit selector to be stepped on to the next contact. The release of the third groupof impulses energizes ROT3 via.

thethird position of wiper W2 of digit selec tor DS', and causes its wipers to bestepped the number of times equivalent to the number of impulses transmitted in the third group.

When the fcalling subscriber is resetting the dial to transmit the fourth digit, the wipers? of "the digit selector are again steppedon to'the nextcon'tact. I Therefore, the fourth group of im-. pulses operate the driving magnet (RoT4) of the fourth number selector via the'fourth position of wiper W2 of digit selector DS, causing its wipers to befstepped a number of times determine'dfby the number of impulses received in the v fourth group.

On the completion of the transmission of the fourthgroup-of impulses,relays D and E remainv energized and relay F is de-energized, which causes the wipers of the digit selector to be stepped on to the fifth position. This causes all the selected lamps'to light through contacts F1, F2, 'through thewiper W3 of the digit selector. to the wipers W4 of the four number selectors, via the selected contactsfland their respective lampsjto the battery. Thus the number dialled by 'theflcalliirg subscriber is displayedfto the exchange operator.

(4') 'EzchcngecstabZishing. a-connection with the called subscriber 'Ha'vingobserved the number displayed by the calling subscriber the exchange operator iii-'- serts-a calling plug -CP into the required subscribers callingf iackMJ, (located in the multiplefiel'd) The insertion of a calling plug into the calling jack lights the supervisory lamp SL thr'oughcontacts H2 H1, contacts L6'L5 and contactsO3O4, after the protectivecalling plug sleeve'relay H and the calling jack cut-off" relay I have operated in series. The operation of relay '1 connects the battery SB at contacts 12 I3 through the called subscribers telcprinter back viathe'ftip connection of the calling pluglandljack CR, -MJ, throughthe windings of j the supervisoryrelay J, contacts H3 H4 and contacts'N'5iN4 to earth.

(5) "Starting ofthe *calZed subscribers teleprinter motor When this circuit is completed the "called" subscribers teleprinter relay. TM is operated. This releases mechanical functions that cause the teleprin-ter, motor to start.

'When, current flows through the previously outlinedlcircuit thefsupervisory relay J is oper- 6 Loop test The operation of relay L breaks contacts L L6 which extinguishes the supervisory lamp SL that was lighted when the calling plug was inserted in the calling jack. I

(7) Automatic release of thecxchcmge display equipment from the cord circuit The operation of relay M causes the display.

pick-up relay C and 'impulsing relay D to become de-energized and so releases them from the cord circuit.

After impulsing relay D has remained deenergized for a certain period the resetting relay E also becomes 'de-energized. With the release of the armatures of relay E-the off normal relay G1 is also de-energized. Acircuit is completed from battery, Ro-Tl and its own contacts 1, 2 resetting wiper of the digit selector contacts E1, E2 to earth- Magnet R01). and its contacts 1, 2, cause the circuit to be self interrupting and the wipers of the digit selector to be rotated thereby to their normal position. When the wipers of the digit selector. cave, their fifth con I tacts the lighted lamps in the display device are extinguished. 'l t hen the wipers: of the digit 18) Exchange indication that connection is completed When the connection has been established the letters Thro are automatically transmitted in the following manner:--

. With the operation of relay L, the release magnet P of the Thro automatic signalling unit is energized through contacts H2 H1, contacts L6, L7, contacts N7 Ndand contacts V5 ,V4. The operation of this magnet causes the contacts Q1 Q2 to reproduce teleprinter impulses that will cause the letters Thro to be typed on the calling subscribers teleprinter, through the following circuit:--

From the signalling battery, through operated contacts I5 I4, through the ring.connection of the calling plug and jack, via contacts H6, H7, via contacts M6 M5, through the ring connection of the answering plug and jack, via con-; tacts B8 B7, contacts I9 I10, through the line to the calling subscribers teleprinter, back via the line through contacts I2, I1,-through contacts B4 B5, through the tip connection of the answering plug and jack, through contacts M2 M3, contacts 02 01, through contacts N2 N1, contacts V7 V6, through transmitting contacts Q1 Q2 to earth.

(9) Exchange operator given indication that connection has been established During the transmission of the letters Thro contacts Q3 Q4: are closed. This causes the Thro connecting lamp TL to glow. On the completion of the transmission of the letters Thro contacts Q3 Q5 are 'closedfor a predetermined interval. This causes relay N' to operate through the following circuitz- Contacts L3 L4, through the windings of relay N,contacts N9 N8, contacts V2 V1, the circuit being completed when contacts Q5 Q3 are closed.

() Completion of connection and the release of the exchange signalling unit When relay N operates, it energizes itself through contacts L4 L3 and N9 N10. The opera tion of relay N also releases the automatic Thro signalling unit from the particular cord circuit, removing the earth Bar and connecting the called and calling subscriber together.

With the operation of relay N, the calling and called subscribers are connected in the following manner From signalling battery, through contacts I5 I4, of the called subscribers equipment at the central station through the ring connection of the calling plug and jack, via contacts H6 H7, contacts M6 M5, through the ring connection of the answering plug and jack, through contacts B8 B7, viacontacts I9 I10, through the line and the calling subscribers teleprinter, back' through the line via contacts I2 II, of the calling subscribers equipment contacts B4 B5, through the tip connection of the answering plug and jack, via contacts M2 M3, contacts 02 01,

contacts N2 N3, through the supervisory relay J, through the tip connection of the'callingplug and jack, through the line to the called subscriber's,teleprinter, back via contacts I213 of the called subscribers equipment and the sig' nalling battery.

(11) Transmission of teleprinier conversation When the previously outlined circuit is established the teleprinter conversation can be effected between the calling and called subscriber.

Before transmitting messages however, it may be desirable for the calling subscriber to receive an indication that he is connected to the correct subscriber to whom he wishes to transmit. This is especially desirable in the present system wherein telegraphic communication can be effected without the intervention of any manual operation on the part of the called subscriber. For this purpose, the means described in United States application No. 519,038 may conveniently be incorporated with the subscribers apparatus whereby the calling subscriber, on depression of a key allotted for that purpose in the transmitter .keyboard or on'transmission of a particular signal, can effect the release of means at the called subscribers station to which he is now connected which will transmit back to the calling subscriber an indication individual to that called subscriber. This indication may conveniently consist of signals representing the exchange name and number of the subscribers apparatus. Similar means may also be provided in conjunction with the exchange equipment whereby a calling subscriber can obtain a positive indication that he is connected to the exchange apparatus before transmitting the indicationof the required subscriber.

.The actual means for effecting these facilitie are not here described but may, readily be ap preciated fromthe description thereof given in the specification of the above mentioned United States application No. 519,038. It will be ap'preciated however that no modification of the present arrangements are necessary when incorporating this feature which adds materially :to the utility and facilities of such a system.

(12) The subscriber clearing an exchange connectr'on Having completedtransmission the subscriber (13) Automatic clearing of a call by subscriber teleprinter To prevent the subscriber holding the line indefinitely after he has concluded his transmission a device isincorporated in the teleprinter which will'clear the call automatically after an idle linc period of approximately two minutes. This device may conveniently be of the type shown in United States Patent No. 1,834,349 whereby after the above mentioned idle line period contacts ACK are opened. The opening of these contacts causes the same functions at the exchange as the operating of the subscribers clearing key CK, and in addition the circuit of the subscribers teleprinter motor MOT is opened to stop the motor.

(14) Exchange operator breaking down connection Having observed the glowing supervisory lamp SL the exchange operator breaks down connection by removing both the answering and calling plugs. This action de-energizes cut-off relay l3, calling jack cut-off relay I'and relay H. When relay H becomes de-energized relays L,

N, O and M also become de-energized, and thus the cord circuit is again in the idle connection.

When the exchange operator inserts a calling plug into the calling jack of the engaged 'line, the

letters Busy are automatically transmitted. This transmission is indicated to the exchange Engage test operator by theglowing of a Busy lamp. The

jack and plug, via contacts H6 H5, through relay R causing relay R to operate. The operation of relay R operates relay S, and the releasemagnet T of the busy automatic signalling unit,through contacts S1 S2. Relay S operates, breaking the operating circuit of relay T at S1, S2 and of relay C at'SS S7. Relay C becomes (is-energized, con, necting the calling vsubscriber to the busy transmitting contacts U1 U2, via contacts-C2 C1 and contacts S5 S6. The BB 1811501! moved InomcontactCS and isappliedviacontocts C7 C6 and contacts 83 S4.

The'positive indication of an engaged test t given by the lighting of the positive engage lamp PEL. When this condition is established teleprinter impulses are transmitted from contacts U1 U2 to the calling subscriber that cause-the" letters Busy to be typed on his teleprinter.

During the transmission of the letters Busy contacts U3 U4 are closed, due to the operating lever descendin from the raised rest position of of the cam. This causes the engaged transmittirng la-mp'ETL to light. Theintroductionpf these two engaged lamps being made for the following reasons-E.-

(a) The ETL lamp gives positive indication that transmission of the letters Busy is in progress. r

' (b) The PEL lamp serves to give positive indication of connection'to an engagedline before and after the transmission of the "letters Busy".

The engaged key letters Busy to be typed on the calling sub" scribers teleprinter, when it is impossible to connect to the wanted subscriber, an engaged key;

EK has been added.

'It is also proposed to use a jack for the same purpose, if required. The depression-of the en gaged key causes the same functions as the operation of relay R.

(17) The calling subscriber wanting connection wifhsupcmisorxor monitoring operator If the calling subscriber requires connection to either the trunk supervisor or the monitor, he will dial-a predetermined number such as 1111".

Upon the receipt of this number the exchange op-' erator would extend the call to the desired position. The setting up of this number operates relay V. The operation of this prevents the transmission of the letters Thro that would otherwise be transmitted when the-call is extended by the operation of the supervisory relay J.

(l8) Calling subscriber wanting trunk connection When a calling subscriber wishes to make n trunk call he will dial a predetermined number such as 2222 and upon reception of this indication the exchange operator would extend the can through to the trunk position. Relay V .is also operated with the reception of. this number, the operation of which prevents the transmission of the letters Thro to the calling subscriber when the call is extended to the trunk position.

(19) Subscriber experiencing trouble when to the calling subscriber when the call is extended to. the monitor s position. Whenextending a call to.-.the monitor's position theoperator depresses the MK key until the off" normal lamp A'I L becomes extinguished.

Alternative arrangements The-following description relates to the extansion of .Ya-trunk caH, that is, to theextensioncl" a call from a subscribers station through the central station cordcircuit of Figs. '1 and 2, the tie line of Fig. 7, and the line jack of Fig. 8 to a called subscribers station associated with an other central station.

(1) The local operator extending a trunk call 'LJAJ at the trunk position.

(2) The automatic starting of the exchange. teleprinter motor by a calling subscriber It is arranged that when the pilot circuit PC is operated by the glowing of any service lamp, the operation of the pilot circuit energizes relay Pl. As this relay is slow acting the operation of thepilot circuit also causes the automatic signalling unit start magnet M1 and teleprinter start relay P2 to be energized for a predetermined impulse period, via contacts 1 and 2 of relay P1.

When all answering keys are in the idle position, a circuit is established through their contacts in series, via the auxiliary windings of the teleprinter magnet ET through contacts 1 and 2 of relay P2 to battery. This circuit holds the exchange teleprinter in the stop condition.

As previously explained with the operation of the pilot circuit. PC relay P2 is energized for an impulse period, which operation breaks the holding current through the auxiliary windings or the teleprinter magnet, thus a starting impulse is produced by the teleprinter magnet which causes the release of mechanical functions that in turn cause the teleprinter motor to start.

(3) The trunk operator answering an outgoing ,call

To answer an outgoing call the trunk operator inserts an answering plug TAP into the tie line jack LJAJ of the glowing calling lamp. This operation causes the relays B and C to operate through the following circuit:

Battery, the windings of relay B, the sleeve connection of plug TAP and LJAJ, the windings of relay 0 to earth.

The operation of relay C de-energizes relay A. This extinguishes the calling lamp JCL and also extends the calling subscriber via the tip connection, contacts B1, B2, through one winding of relay X to battery and via the ring comnection, through contacts B5 B6 contacts E6 E7, and contacts E9 E10 in parallel, contacts E4, E3, contacts K9 K10 through the windings of relay D to earth.

(4) Automatic connection of the exchange startstop apparatus When current flows through this circuit relay D is operated, and it looks itself energized through contacts B3 B4, contacts D7 D6, through the contacts of the trunk calling key, the contacts Ll L2, to the battery.

The further function achieved with the operation of relay D is the operation of relay E which is energized through contacts D5 D4, via

contacts of the answering key AK and trouble key TK to earth. I

With the operation of the relay E the operating circuit of relay D is broken at contacts E3 E4, but

earth is maintained on the "calling subscriber's line through contacts E4, E5, and contacts D1'D2.

(5) The automatic transmission of start-stopimpulses when exchange'apparatus enters the circuit The closing of contacts E1 E2 controls the transmission of the start-stop impulses that cause indication to be typed on the calling. subscriber's teleprinter that the exchange receiving apparatus is in circuit. v

The closing of contacts ELEZene'rgizes relay F and magnet M2 through contacts F2, F1. The energizing of magnet M2 causes the required teleprinter impulses to be reproduced on contacts G1'G2. With the operation of relay Ethe calling" subscribers circuit is extended'through contacts E10, E11, via contacts G1 G2, contacts L3 L4, contacts R3 R4, through the teleprinter relay magnet ET, through the teleprinter transmitter XMTR, through contacts E8 E7, contacts E4 E5, contacts D2 D1, to earth; 7 Therefore, the teleprinter impulses reproduced by contacts G1 G2 are recorded on both the calling subscriberand exchange teleprinters.

(6) Subscriber giving number required Having received the typed indication that the exchange teleprinter is in circuit the subscriber then transmits teleprinter impulses that cause the number of the subscriber with whom he wants connection to be typed up on the exchange teleprinter.

(7) The trunk operator calling the required exchange Having observed the number and exchange of the wanted subscriber the exchange operator throws the answering key AK to the trunk" calling side. 'ICS. This breaksthe locking circuit of relay D, thus causing it to become cleenergized. The de-energizing of relay D deenergizes relay E and also causes relay M to operate through the following circuit:-'

Battery, the windings of relay M, contacts of answering key AK (trunk calling side TCS) D3, D4, through contacts of answering key normal side NS and trouble key TK to earth through all answering keys in series.

.The operation of relay M and the de-energizing of relay E removes'the earthconnection of the calling subscriber from contacts E4 to contacts M4 M5. The circuit of the calling subscriber following the operation of relayM is asfo1lows:.-

From the signalling battery SBthrough one winding of relay X, via contacts B2, B1, through the tip connection to the calling subscriber, back via the ring connection throughcontacts B5 B6, to contacts E10 E9 and E7 E6 in parallel, contacts M4 M5 to earth. V

The operator having observed the exchange to which connectionis required inserts the. calling plug TCP in'the line jack TCJ (Fig. 8) of a trunk line connected to the required exchange. Inserting the calling plug, TCP into the trunk line jack TCJ, relays H and T are energized in series. The operation of relay T breaks the spacing current from the transmitting relay TR by interrupting contacts T1 andT2. The transmitting relay TR has a permanent bias to is removed, due to the permanent bias to mark,

1 this relay operates to mark. A marking current :fis'then transmitted from contacts TR2, to the'centre point of the differential milliammeter MA, passed differentially through the receiving relays RRl, RRz, over the trunk line through the receiving relays at the distant exchange and'back tcthe centre point of the transmitting battery. The marking of the receiving relays at the distant end causes the calling lamp corresponding to TCL at that end to glow. (:8) Exchange answering "incoming trunk calls As previously explained, to call the distant exchange the marking current is signalled over the line. The arrival of this marking current marks the unbiassed (neutrally set) receiving relays -RR1 RRz, the operation of which causes call- .ing lamp TCL to glow,-by energizing calling relay N through the following -circuit: I

Contacts RR12, EH13, contacts T4 T3, calling relay N.

The exchange operator observing a glowing :"fcall-ing lamp inserts an answering plug TAP .into the respective line jack. This function causes relays B-a'nd T 'to operate in series.

-As previously described relay D operates, causing relay E to operate. The operation of relay E releasing the transmission of indication that the exchange teleprinter is in circuit. After receiving the wanted subscribers number he inserts the calling plug 'I'CP. into the required :subscribers calling jack MJ (Fig. 3). wifcaving the "ca-Siam exchange the number of wanted subscriber The arrival of the marking current from the distant exchange marks the receiving relays RRi and RRz. This establishes the exchange teleprinter circuit and the received teleprinter impulses that are thus recorded by the operation of the following:circuit:--.

Contacts R323, RRz2,: through one Winding of the transmitting relay TR, via the tip connecti'on of the connecting plug and jack, through contacts H6, H7, through winding of the supervisory relay I,'through contacts 06,07, of the disconnect relay ,0, through contacts M2, M3,

through exchange teleprinter transmitter XMTR and teleprinter magnet ET, through contacts R3, R4, contacts M8,

earth. 7

Having received typed indication that the M7, contacts M4, M5, to

distant exchange teleprinter is in circuit the calling exchange operator then types-the number 0t the. wanted subscriber. After which the answering key AK can be thrown to the. idle position, which will .deenergize relay M and relasethe home exchange teleprinter from the called circuit. v

starts the called subscribers teleprinter and when current flows relay J is operated. The functions previously outlined cause the transmission of teleprinter impulses thatrindicate in typed cha'racterson the calling .subscribers :CKF (drawing Fig. 4).

' mark. Consequently, when" the "spacing current teleprinter that connection has been completed in the'following manner:-

The; operation of relay I operates relay J through one winding of relay H, contacts 11, 12,

through relay J. The operation of relay J releases the through indication by establishing the following circuit:

' From earth, via springs of answering key, contacts J1,:J2, contacts K1, K2,winding of magnet M3 to battery.

The operation of magnet M3 causes the required teleprinter impulses to be reproduced on contacts L3, L4. The-operation of relay J also energizes relay K, through contacts J4, J5,

and relay K. The operation of relay K breaks the through release circuit at contacts K1, K2, but not in time to prevent M3 being operated.

Relay K locks itselfenergized, through contacts B3, B4, contacts K3, K4. The operation of relay K also ex'tinguishes the supervisory lampSL that lights when a calling plug is inserted in callingjack MJ, by breaking contacts K5, K6.

The operation ;of relay K also breaks the op erating circuit of relay Dby breaking contacts At the termination of the required 2! K9, K10. transmission from contacts L3, L4, contacts L1, L2 are open for a predetermined time. The opening of these contacts interrupts the locking circuit of relay D which becomes de-energized. The de-energizing of relay D causes relay E to'become de-energized and so releases the exchange teleprinter from the cord circuit, com pleting connection. a

The cord circuit relay X is designed so that it will not operate when equal value currents flow throughthe two main windings. When the current in one winding exceeds that of the other,

by a predetermined value relay X operates.

It willbe understood that means may also be incorporated with the subscribers apparatus in this arangement also whereby the calling subscriber, on causing the transmission of a particular signal, can obtain an indication individual to the subscribers apparatus to which he has been connected. This may be printed on the calling subscriber's teleprinter receiver in the same way as the other indications which notify him of the progress of the call. These means have "been referred to above in the description with reference to Fig. '4.

(11) The subscriber calling in the exchange operator When the subscriber wishes to call in the exchange operator he depresses his calling key This causes relay X to operate due to the unbalanced condition produced by different values of current traversing its main windings.

The operation of relay X lights the flashing lamp FL through contacts H4, H5, contacts J6 J7, holding windings of relay X, contacts X2 X1, via contacts of the answering key. When this circuit is established the current flowing serves to lock the relay X in the operating condition.

(12) Engage test at a trunk position If a calling plug is inserted in the calling jack of an engaged line teleprinter impulses are transmittedthat cause the indication to be typed on the calling subscribers teleprinter that the wanted line is Busy. iThis is achieved in the following manner:

The insertion of the calling plug TCP in the calling jack of an engaged line causes relay P to become energized. The operation of relay P operated relay Q and magnet M4, in parallel. The operation of magnet M4 causesthe required impulses to be produced on contacts R3 R4, that will cause the necessary indication to be typed on the calling subscribers teleprinter.

If connection cannot be made to the wanted subscriber, teleprinter impulses can be released that will cause such information to be indicated in typed characters to the calling subs'cribers teleprinter by inserting the calling plug into a particular jack or operating a key.

The following is the, method of operation of the circuit arrangements of Figures 9, -10, l1 and 12. These arrangements as previously mentioned, operate on similargeneral principles to those of Figs. 1, 2, 3 and that a simplification thereover is shown together with some additional features.

Subscriber calling exchange Subscriber given indication that he has cailecl the exchange When current flows in the above circuit the needle of the subscribers indication meter SIM, will point to exchange called.

Exchange answering calling subscriber To answer a call the exchange operator inserts an answering plug AP of a connecting cord (Fig. 11) into the answering jack AJ of theglowing calling lamp CL. This operation energizes the cut-off relay B and the display pickup relay C in series through the following circuit.

Earth, winding of relay B, sleeve connection of answering jack and plug AJ, AP., contacts M8, M7, contacts S2, S1, winding of relay C to battery.

Upon the insertion of the answering plug AP intothe answering jack AJ a holdingpotential is applied to relay A at contacts AJ .1, AJ .2, so that upon the operation of relay B relay A is not de-energized. The operation of relay B, however, extinguishes the calling lamp CL by in terrupting its circuit at contacts B7, B8.

The operation of relays B and C connects the impulsing relay D of the exchange display equipment to the calling subscribers equipment by establishing the following circuit: I

Earth, contacts Z3, Z4, exchange indication meter E.I.M., winding of relay D, contacts C3, C2, contacts M1, M2, tip connection of answering plug and jack AP, AJ, contacts A7 A6, contacts B6, B5, via the line through the subscribers equipment, back via contacts B2, B3, contacts A9, A10, ring connection of answering jack and plug AJ, AP, contacts M5, M4, contacts C5, C6 via a resistance to battery.

When current traverses this circuit the calling subscribers motor is started due to the operation of the teleprinter' magnet TM., and the needle of his indication meter pointsto dial thus giving him indication that hecan dial the wanted number. 1

Also with the operation of relayD, relay E is energized via contacts D2, D3; v In operating, relay E removes the resetting potential irom the selector wipers W1 by opening contacts E2, E1.

The calling subscriber giving the number of the wanted subscriber In order to display the wanted number at the exchange the subscriber dials two groups of impulses, these groups causing relay D to operate a certain number of times. -During the first group of impulses each operation of relay D operatesthe first number selectormagnet (ROT.2)

a certain numberof times corresponding to the number of impulses recorded on relay D. This is achieved through the following circuit? Earth, contacts D2, D1, contacts E5, E6, winding of digit selector relay '3, first contact position of Wiper W2 of the digit selector DS, windings. of the first number selector magnet (ROTZ) to battery.

The transmission of the first group of impulses through the first number selector magnet (ROT.2) causes the wipers of the first number selector N81 to be set round to a position determined by ,the number of times ROT.2 isenergized. I

The transmission of this first group of impulses through the digit selector relay F causes it to. operate, and energize through contacts F2, F3, the driving magnet ROT.1 of the digit selector DS.

Consequently, the number of steps made by the first number selector N81, are the same as the number of impulses signalled in the group. At the end of the transmission of the first group of impulses representing the first digit, the subscriber operates his dial to transmit the second digit. During this time the impulsing relay D and relay E remain energized and relay F is deenergized. When relay F becomes de-energized,

the digit selector driving magnet (ROTJ) is also de-energized. Thiscauses the contact arms or so-called wipers of the digit selector to be stepped one division, or in other words, on to their next contact.

When the calling subscriber releases the dial to transmit the second digit group of impulses, the relay F is again energized in series with the driving magnet of the second number selector ROTB) via the second position of the wiper W2 of the digit selector DS. The driving mag- On the completion of the transmission of the second group of impulses relays D and E remain energized and relay F is again de-energized, causing the wipers of the digit selector to be stepped on to the third position. This causes the two selected lamps to light, through the following circuit:

Earth, contacts F2, F1, wiper W3 of the digit selector, wipers W2 of the two number selectors, via the selected contacts and their respective lamps to battery. Thus the number dialled by the calling subscriber is displayed to the exchange operator.

The exchange operator establishing connection with the wanted subscriber Having observed the number displayed by the calling subscriber, the exchange operator inserts a calling plug CP into the requiredsub scribers calling jack CJ. The insertion of the calling plug CP into the calling jack GJ energizes relays H and B through the following circuit:

From battery, one winding. of relay H, ring connection of the calling plug and jack CP CJ, winding of relay B, to earth.

With the operation of, relay H the supervisory lamp SL lights through contacts H2, H1, contery SB, contacts A5, A6, contacts B6, B5 via the loop through the called subscribers' equipment back via contacts B2, B3, contacts A9, A8, via the tip connection of the calling plug and jack CP, CJ, contacts H5, H6, winding of supervisory relay J, contacts N4, N5, via a resistance to the negative pole of the signalling battery.

When current flows through this circuit the supervisory relay J v is energized and the called subscribers teleprinter relay TM is op- 'erated, releasing mechanical functions that cause his teleprinter motor to start.

The energizing of the supervisory relay J causes it to operateand to close the energizing circuit of relay K, via contacts J2, J1, contacts H1, H2.

Relay K, in operating, energizes relays L and M through the following circuit:--

Earth, contacts K2, K3, the windings of the respective relays to battery.

It also prepares an energizing circuit for relay N at contacts L3, L4 which is completed after the transmission of the letters Through to be explained hereafter. The operation-of relay L also extinguishes the supervisory lamp SL by opening contacts L6, L5.

The operation of relay M connects the calling subscribers circuit to the Through transmitting unit at contacts M2, M3, and retains battery on this circuit via contact M5, M6, contacts H4, H3, sleeve connection of the. called subscribers calling plug and jack CP, CJ, contacts A11, A12, to battery.

Calling subscriber given indication that connection is completed When the connection has been established the letters Through are automatically transmitted in the following manner. With the operation of relay L the release magnet P of the Through automatic signalling unit is energized through the following circuit:

Earth, contacts H2, H1, contacts L6, L7, contacts N10, N9, windings of magnet P to battery.

The operation of this magnet causes the contacts TTl, TT2, to produce teleprinter impulses that will cause the letters Through to be typed on the calling subscribers teleprinter through the following circuit:

Earth, contacts TTl, TTZ, contacts N1, N contacts 01, 02, contacts M3, M2, tip connection of answering plug and jack AP, AJ, contacts A7, A6, contacts B6, B5, via the loop through the calling subscribers equipment back via contacts B2, B3, contacts A9; A10, ring connection of answering jack and plug AJ, AP, contactsMB, M6, contacts H4, H3, sleeve connection of calling jack--and plug CP, CJ,

signalling battery.

contacts A11, A12, to the negative 7 pole of the Exchange operator given indication that conneclion. has been established During the transmission of the Through, contacts TT3, TT, are closed causing the through connection lamp TL to glow.

Extending the callto the wanted subscriber The calling subscriber verifying'erchange connection After the reception of the indication that he ls through and wishing to'verify that the exchange has connected him to the required number/the calling subscriber can, by depressing his Whov are you key, cause the called subscribers teleprinter to transmit'teleprinter 1mpulses that will cause its exchange number to be printed on the calling subscribers teleprinter.

Automatic release of the exchange display equipment from the cord circuit (a) Upon the energization and operation of supervisory relay J following the insertion of the calling plug CP into the calling jack CJ, relay K is energized via contacts J1, J2." This completes a circuit through relay M via contacts The operation of relay M causes the display pick-up relay C and therefore impulsing relay D to become de-energized and releases them from the cord circuit by opening contacts M2, M1, M8, M7. The operation of relay M also causes relay B to be connected in series with the locking Winding of relay Hso that upon the clearing of the call the supervisory lamp is not extinguished until both plugs have been removed.

letters (b) After impulsing relay D has remained v de-energized for a certainperiod, the resetting relay E also becomes de-energized. The opening of contacts E2, E3 de-energizes the off-normal relay G. Relay E being de-energized, causes a resetting potential to be applied to theresetting wiper W1 of the digit selector through contacts E2, E1, and windingsof relay W. This causes the wipers of the digit selector to be rotated to their normal position. When the-wipers of the digit selector reach the normal position a potential is applied to the resetting wiper W1 of the first number selector via. contacts G2, G1} This causes magnet ROTZ to rotate the wipers of the first number selector N81 to their normal position. When the wipers of the first number selector reach the normal position a potential is applied to the resetting wiper Wlof the second number selector NS2, causing magnet ROT3 to rotate the wipers of the second number selector NS2 to their normal position.

(0) While the above operations are taking place relay W is energized and in operating energizes relay Z via contacts W2, W1. Upon operat- Exchange receiving indication when connection is disengaged "Having completed transmission, either subscriber'depresses his clearing key CK which immediately clears the connection at the exchange and lights the supervisory lamp in the following manner: I 5 f After thefcalling or called; subscriber depressed his clearing key CK for' a-predetermined period, the supervisory relay J becomes de-energized, de-energizing relay K. Relay 0 is then energized viacontacts K2, K1, contacts L1, L2, relay L stillbeing energized. The operation of relay 0 causes the supervisory lamp SL to glow via contacts 05, 04; The line circuit is also interrupted at contactsO2, 01, so that upon the release of the clearingkey relay J is not again energized. z

Automatic clearing of exchange connection To prevent-the subscriber holding the line indefinitely after he has concludcd'hi's transmission, a. device is incorporated in the teleprinter by s which a call will be automatically cleared after anidle line period of approximately two minutes.

. The opening of a pair of contacts by this device causes the same functions at the exchangeas the operation of thesubscribersclearing key CK and in addition the motor circuit of the subscribers teleprinter is opened stopping the motor.

The sequence of operation of the contacts. by this device is as followsz-Upon the automatic operation'due to the action of the call clearing device a predetermined intervalafter cessation of signalling, contacts ASl, AS2 are opened clearing the line, just prior to the openingof contacts ASS, A56, causing the stopping of the motor. Upon. the opening of contacts ASS, AS6, contacts ASS, AS4, are closed'preparing the 'subscribers circuit for the next call. Upon receipt of the first impulse of the next call, contacts ASI, AS2 are closed immediately followed by the opening of contacts A53, A84, and the closing ofv contacts AS5, ASS, the latter efiecting the starting of the teleprinter motor.

Exchange operator breaking down connection at the exchange I Having observed the glowing supervisory lamp SL the exchange operator breaks down the connection by removing both the answering and calling plugs. This i action de-energizes relay B and relay H. With the tie-energizing of relay H, relays L, M, N and 0 also become de-energized and thus the cord circuit is again in the idle condition. The de-energizing of relay 0 extinguishesthe supervisory lamp SL by openingcontacts O4, O5.- It should be noted that relay H cannot be de-energizedand therefore the supervisory lamp SL extinguished until both plugs are re- When the exchange operator is asked for a subscriber whosejlineis' engaged, she depresses her engaged key EK and teleprinter impulses are automatically transmitted, causing t.e letters Busy to be printedfo'n the calling subscribers teleprinter. This transmission is indicated to the exchange operatorby the glowing oi the busy transmission'lamp The automatic' transmission of the letters Busy is achieved in the following manner: Upon the depression of the engaged'key EK relay S and magnet T 'are'energized in series. Relay S operates and breaks the operatingcircuit of relay C at contacts S1, S2. ,Relay C becomes tic-energized connecting the calling subscriber to the busy? transmitting contacts BT1 BT2 via contacts S5,'S4, contacts ;C1,C2. Battery is removed from contact C6 and applied to contact C4 via contacts S10, S11, With the operation of relay S the energizing circuit of relay B'is'retained through the locking winding of relay S via contacts S2, S3. i The operation of relayS also causes the engaged transmitting lamp ETL to glow via contacts S6,, S7; At the completion of the trans: mission of the letters Busyfcontacts VI 1,-BI 2 are closed energizing relayU via contacts S9, S8. In operating, the relay locks itself viacontacts U1, U2 and remains energized until relay S is de-energized. Q v H Upon operat relay U lights the positive engaged lamp PEL via contacts U3, U4 giving the operator.v positive indication that the letters Busy have been transmitted. 1 After the lighting of the positive engaged lamp PEL;the operator removes the answering plug AP irom the answering jack AJ thus de-energizing cut-10ft relay B and relay S, and thereby de-energizing relay U and extinguishing the positive engaged; lamp PEL. Subscriber obtaining telepm'nter connection ithe exchange Should the subscriber require teleprinter conversation with the exchange, he will dial a prewith determined-number, upon the reception of which the operator will connect him through to the operators position in an identical manner with that when connecting through tofanother subscriber.

clearing a call before the exchange operator has answered I If, after calling the exchange and before bein answered, the subscriber decides that he does not want to make the call, he will depress his clearing key CK and thus interrupt the energizing circuit of his calling relay'A. This relay is de energiz'ed and his calling lamp CLI is extinguished thereupon. I Subscriber clearing due to nits-dialling Should the subsc'ribermake a mistake whilst dialling the number he requires, he will depress his clearing key GK and thus interrupt the energizing circuit of impulsing relay ,D' caus- Subscriber ing it to: become dee'ne'rg'iz'ed. This, in turn, 'will de-energize relay E which will apply.a.re-.

setting potential tothe resetting wipers of the selectors via the winding of relay W asexplained aboveipara. 10) and theselectors will be returned to normal, v

Relay W being energized operates and energizes relay Z which locks itself through the following circuit:

Earth, contacts D2, D1, contacts E5, E4, contacts C8, C7, contacts Z2, Z1, winding of relay Z to battery.

In operating, relay Z removes earth from the fimpulsing relay D by opening contacts Z3, Z4 and therefore the calling subscriber cannot effect its operation by further dialling.

With the operation of relay Z the dial clearing lamp DCL is also lighted via contacts Z6, Z7.

Seeing the glowing dial clearing lamp DCL the operator removes the answering plug AP from the answering jack AJ which de-energizes relay 0. In becoming de-energized relay C interrupts the energizing circuit of relay Z at contacts C7, G8, which uponbecoming de-energized connectsearth again to the impulsing relay D at contacts Z3, Z4. At the same time the dial clearing lamp DCL is extinguished due to the opening of contacts Z6, Z7.

What is claimed is:

1. In a telegraph system, a central intercom necting station, a source of signalling current thereat, a plurality of subscribers stations, a line circuit between said central and each of said subscribers stations, a relay at the central station operable in response to, an earth condition on the line circuit for indicating a calling signal, a cord circuit at the central station connectable between any two of said subscribers stations, and a second relay in said cord circuit normally energized during telegraphic communication therethrough but responsive to a break signal of predetermined minimum length of time forindieating a clearing. signal. V

2. In a telegraph system, a subscribers station, a line circuit signal transmitting and receiving apparatus, a source of mechanical power for driving said apparatus, electro mechanical means'responsive to the first current impulse in said line circuit for starting said mechanical power and to stop said power a predeterminedinterval of time after the cessation of signalling impulses, a key for earthing the line circuit for sending a calling signal, and other key means also operated by said electro-mechanicalmeans to open said line circuit for sending a clearing signal.

3. In a telegraph system, a plurality of subscribers stations, a central interconnecting station, a line circuit connecting each of said subscribers stations to said central station, a cord circuit through which any two subscribers stations can be connected to the central station, a relay individual to each line circuit at the central station and operable in response to an earth condition on the corresponding line to indicate a calling signal, a second relay in saidfcord circuit operable on connection of any two subscribers stations therethrough and responsive to a break signal exceeding a predetermined length for indicating a clearing signal, the first said relay also being responsive to said break signal before the connection of the cord circuit to the subscribers line, for discontinuing the calling signal.

4. In a telegraph system, a central interconnecting station, a source of signalling current thereat, a plurality of subscribers stations each comprising a telegraph signal receiving relay, telegraph" signal transmitting contacts and dialling impulse transmitting contacts connected together in series in a normally closed circuit at the subscribers station, a resistance connected across said dialling impulse contacts for maintelegraph apparatus, driving means therefor and an impulsing dial, a central station to which each of said subscribers stations is connected bya line circuit, said central station having an answering and a calling jack associated with each subscribers line circuit and a cordcircuit co-operating with said jacks, a displayequipment associated with said cord circuit, and means responsive to the connection of said'cord circuit with the answering jack of a calling subscriber-tor placing said display equipment under control of the .impulsing dial and for starting the driv means at said subscribers station.

6. In a telegraph system, a plurality of subscribers stations, each provided with an impulsing dial, a centralstation to which each of said subscribers stations is connected by a line circuit, said central station havingan answering and a calling jack associated with each line circuit, and a .cord circuit provided with a pulsing circuit, a display device associated with said-cord circuit, said device comprising aseries of number indicators, a corresponding, series of number 1 a switches each having a motor magnet and adapted to complete an operating circuit for any one of the corresponding number indicators, a digit selector switch having a motor magnet and adapted to successively associate the motor magnets of consecutive number switches with said pulsing circuit, a slow-release relay in said pulsing circuit adapted to complete an operating cir-' cuit for the motor magnet of the digit selector switch at the end of each series of impulsestransmitted through said pulsing circuit, and

means responsive to the connection of said cord circuit with the answering jack of a callingsubscribers line circuit for placing said cord puls-' ing circuit under control of the calling subscribers impulsing dial.

7. In a telegraph system, a calling and a called subscribers station, a printer at each of said stations, a central'station through which said sub:

scribersstations can'be interconnected, means for establishing a connection from a calling to a called subscribers station in a plurality of stages,

and means at the centralstation responsive to the progress of operations in extending a call from the calling to the called subscribers station for transmitting progress signals to the printer at said calling subscribers station at more than on stage in said progress of operation.

8. Ina telegraph system, a plurality of subscribers stations having transmitting and receiving apparatus, a central interconnecting station, a link circuit thereat through which any two of said subscribers station can be connected, the connection between two stations being established in a plurality of stages, andmeans associated with said link circuit to transmit progress signals composed of groups of impulse combina-' tions to a calling subscriber for indicating the progress of a call which signals are transmitted at more than one stage of the call progression and are translated and printed on the receiving apparatus normally provided for telegraph communication. l

'9. In a telegraph system, a plurality of subscribers stations having transmitting and receiving apparatus-in series in a line-circuit, a central station, a cord circuit thereat having a calling and an answering plug for connecting any two of said subscribers stations therethrough, relay means associated with said cord circuit responsive to the completion of a circuit to a called subscriber through said calling plug, signalling means controlled thereby to send a through-indication to a calling subscriber throughsaid answering plug, and other relaymeans operated on completion thereof to; disconnect said signalling means and'to'complete the circuit between said two subscribers stations.

'10. In a telegraph system, a subscribers station, a central station to which said subscribers station is connected by a line circuit, a first cord circuit at the central stationto whichsaid subscribers station can be connectedasecond cord circuit, a tie line for connecting said first and second cord circuits, transmitting and'receiving apparatus at said subscribers station, motor means associated with said receiving apparatus and operable in response to the connection of said subs'cribers station to said first cord circuit, transmitting and receiving apparatus associated with said second cord circuit, motor means associated with said cord circuit receiving apparatus and operable in response to the connection of said first cord circuit to said tie line, said'cord circuit receiving apparatus being efiective to receive an indication of a required subscriber's number from said subscribers station when the second cord circuit is connected to said tie line.

11. In a, telegraph system, a subscribers station provided with aprinter and driving means therefor, a central station to which said subscribers station is connectedlby a line circuit, a first and a second cord circuit and a tie line at the central station, a printer and driving means therefor associated withthe second cord circuit, a normally closed locking circuit for holding said last mentioned driving means inoperative, a start relay for controlling said locking circuit, means responsive to the connection of the first cord cirthe driving means at the subscribers station and for extending the subscribers line circuit to the first cord circuit, means responsive to the connection of the first cord circuit to the tie line for energizing a pilot circuit and extending said subscribers line circuit to the tie line, said start relay being operated in response to the energization of said pilot circuit to render said driving means operative, and means responsive to the connection of the second cord circuit to the tie line for interconnecting the printer at the subsc'ribers station and the printer at the second cord circuit.

12. In a telegraph system, a central station having a plurality of cord circuits, a corresponding plurality of keys, transmitting and receiving apparatus for telegraphic communication and connectable to any of said cord circuits through the corresponding one of said keys, a source of mechanical power for, driving said apparatus, means for controlling said source of mechanical power and operated by a signal receiving magnet in said receiving apparatus, an auxiliary winding in said magnet and energizable through all of said keys in series to hold said means in a stop position for said power, and a pilot circuit energized on receipt of a calling signal to send an impulse through said keys and auxiliary winding to start said source of power.:

13. In a telegraph system, a plurality of subscribers stations having signal transmitting'and receiving apparatus, a line connecting said central to each subscriber's station, a source of mechanlcal power for each of said subscribers apparatus, control means for said power and operable on response of the'subscribers receiving apparatus, to' the first impulse received over the line-circuit, a key for earthing said line for a predetermined minimum interval of time, relay means at the central station operable in response thereto and thereafter maintained operated under .local control, other key means for breaking said line circuit fora predetermined minimum in terval, and a supervisory relay in each cord cir-fl cuit operable on connection of any two subscribers stationstherethrough and responsive to said break in the line circuit for indicating a clearing signal.

14. In a telegraph system the combination as set forth in claim 13 together with other relay means operated by said supervisory relay for independently breaking the line current through the cord circuit and'for lighting a signal lamp.

15. A telegraph system comprising a plurality of subscribers stations each having telegraph signal transmitters and receiving apparatus, dialling t impulse transmitting means and break signal key means allin series in a line circuit, a key for earthing the line circuit for sending a calling signal and power driven means for said telegraph apparatus under the control of signal currents received over the line circuit, a central interconnecting station-having a plurality of cord cir cuits, a source of signal current, relay means responsive to an earthing signal in each subscribers line circuit, means to connect one side of a cord circuit to a calling subscribers line, a display equipment, relay means to connect said equipment to said cord circuit on connection to a calling subscribers line, means to connect the other side of said cord circuit to a required subscribers line, and relay means in said cord circuit operated on completion of a circuit to' a required subscriber torelease said display equipment and to complete a telegraph circuit through both sides of said cord circuit.

16. In a telegraph system, a calling subscribers station associated with a first central station, a called subscribers station associated with a sec and central station, each of said stations being provided with a printer and driving means there- 'for, means for interconnecting the printer at the calling subscribers station with the printer at the first central station and for starting the driving means therefor, means for subsequently disconnecting said connected printers, means for then connecting the printer at the first central station with the printer at the second central station and for starting the driving means for the latter of these printers, means thereafter effective for disconnecting the printer at the first central station'from the printer atthe second central station, for stopping the driving means for the former of these printers, and for connecting the printer at the calling subscribers station with the printer at the second central station, and means finally eiTective for disconnecting the printer at the second central station from the printer at the calling subscriber's station, for stopping the driving means for the former of these printers, for interconnecting the printer at the calling subscribers station with the printer at the called subscriber s station andfor starting the driving means for the last mentioned printer. p 1

17. In a telegraph system, a subscribers station associated with a central station, a first and a second cord circuit and a tie line at the central station, a printer and driving means therefor associated with the second cord circuit and another printer and driving means therefor at the subscribers station, a code transmitting device likewise associated with the second cord circuit, means for starting the driving means at the subscribers station when the first cord circuit is connected to the subscribers station to indicate that connection has been established, means for starting the driving means for the cord circuit printer when the first cord circuit is connected to the tie line, and means effective when the second cord circuit is connected to the line for causing the code device to operate the calling subscribers printer to indicate that connection has been established to the second cord circuit. a

18. In a telegraph system, a subscribers station associated with a first central station,a trunk cord circuit at said central station, a printer with driving means therefor at said subscribers station and another printer with driving means therefor associated with said trunk circuit, a second central station associated with the first central station, a trunk cord circuit thereat provided with an associated printer with driving means therefor and an associated code sending device, means effective when the calling subscribers station is connected to the trunk cord circuit at the first central station for connecting the printer at the calling subscribers station to the print,- er associated with the trunk cord circuit and for starting the driving means for thislatter printer, means at the first central station for connecting the cord circuit printer in the trunk cord circuit and disconnecting the printer from the subscribers printer, and meanseffective when-the first central station trunk circuit is, connected to the second central-station cord circuit for interconnecting the first and second central station printers, for starting the driving means forthe printer at the secondcentral station and for ac-,

tuating the code sendingdevice to operate the circuit through which any two subscribers stations can be interconnected, a code sending device associated with said cord circuit, means effective when said cord circuit is connected to a calling subscribers station for starting the driving means thereat and for connecting the subscribers printer to said cord circuit, means responsive to the connection of the cord circuit to a busy subscribers station for placing the calling subscribers printer under control of the code sending device and for actuating said devices to send busy signals to the subscribers'printer, supervisory means at the central station responsive to the connection of the cord'circuit to the busy subscribers' station and other supervisory means operable during the actuation of said code sending device. 7 I a a 20. In a telegraph system, a calling and a called subscribers station. a printer-at each of said stations, a central station through which said subscribers stations can be interconnected, means for establishing a connection between calling and called stations in a plurality of stages,.means responsive to the progress of operations in extending a call from the calling to the called subscriber's station for transmitting signals indicative o! the progress at more than one stage of the call progression, and means for causing said transmitted signals to operate the printer at the calling subscribers station to record such stages of progress.

RONALD GEORGE GRIFFITH. 

